1. Field of the Invention
The present invention relates to a method of manufacturing an electrophotographic photosensitive member which comprises a functional film formed on an aluminum substrate and, more particularly, to an electrophotographic photosensitive member which is made up by forming a non-monocrystalline deposited film comprising silicon atoms and hydrogen atoms on an aluminum substrate comprising a silicon element as a functional film according to a plasma CVD method and a method of manufacturing the member.
2. Related Background Art
Glass, heat-resistant synthetic resin, stainless steel, and aluminum have been proposed as substrates for forming deposited films of electrophotographic photosensitive members. Actually, however, metals have often been used for their durability to electrophotographic processes such as charging, exposure, development, transfer and cleaning and for maintaining high positional accuracy at all times without deterioration of an image quality. Particularly, aluminum is one of most suitable materials for substrates of electrophotographic photosensitive members for its excellent workability, low cost and light weight.
A technique regarding those materials for the substrates of the electrophotographic photosensitive member is described in Japanese Patent Application Laid-open No. 59-193463 and Japanese Patent Application Laid-open No. 60-262936. Japanese Patent Application Laid-open No. 59-193463 has disclosed a technique for obtaining amorphous silicon electrophotographic photosensitive members which provide a high image quality by forming supports with aluminum alloys which have a Fe content of 2000 ppm or less. In addition, this laid-open application has disclosed a procedure for forming amorphous silicon by glow discharging after cutting a cylindrical (or cylinder-like) substrate by means of a lathe and mirror-finishing its surface. Japanese Patent Application Laid-open No. 60-262936 has disclosed an extrusion-molded amorphous silicon aluminum alloy, comprising Mg of 3.0 to 6.0 weight % and Mn of not more than 0.3 weight %, Cr of less than 0.01 weight %, Fe of not more than 0.15 weight % and Si of not more than 0.12 weight % as additive impurities, and the remainder comprising aluminum, which excels in depositability. However, these laid-open applications do not disclose a cleaning method with water containing specific substances.
Japanese Patent Application Laid-open No. 61-171798 has disclosed a technique regarding a method of working substrates for electrophotographic photosensitive members. This laid-open application has disclosed a technique for obtaining an electrophotographic photosensitive member made of high quality amorphous silicon or the like by cutting a substrate with a cutting oil of specific contents. This laid-open application has also disclosed that the substrate is cleaned with triethane (trichloroethane: C.sub.2 H.sub.3 Cl.sub.3) after cutting.
Techniques regarding surface treatments of substrates of electrophotographic photosensitive members have been proposed in Japanese Patent Application Laid-open Nos. 58-014841, 61-273551, 63-264764 and 1-130159.
Japanese Patent Application Laid-open No. 58-014841 has disclosed a technique for obtaining a uniform oxide film by removing a natural oxide film on a surface of an aluminum support and immersing it into water with a temperature of not less than 60.degree. C.
Japanese Patent Application Laid-open No. 61-273551 has disclosed a technique including alkali cleaning, trichloroethylene cleaning and ultraviolet ray irradiation cleaning with a mercury lamp, as pretreatments of substrates, for forming an electrophotographic photosensitive member by depositing Se or the like on an aluminum substrate and has also disclosed cleaning with degreasing liquid, steam and purified water to remove oil and fat remaining on the surfaces of cylindrical aluminum substrate, as a pretreatment for ultraviolet ray irradiation cleaning.
Japanese Patent Application Laid-open No. 63-264764 has disclosed a technique for roughing the surface of substrate with a water jet.
Japanese Patent Application Laid-open No. 1-130159 has disclosed a technique for cleaning a electrophotographic photosensitive support with a water jet. Though this laid-open application has disclosed amorphous silicon simultaneously with Se and organic photoconductive materials as an example of the photosensitive member, no problems inherent to the plasma CVD method have been discussed.
On the other hand, Japanese Patent Application Laid-open No. 60-876 has disclosed a technique for blowing carbon dioxide into super purified water as a pretreatment for substrates other than electrophotographic photosensitive members to prevent damage due to static discharge on wafers. However, this technique provides an antistatic measure against static electricity produced on substrates with a high resistance as wafers and is not described for use conductive substrates such as of aluminum.
Various types of materials including selenium, cadmium sulfide, zinc oxide, amorphous silicon and organic substances such as phthalocyanine have been proposed as the materials for the electrophotographic photosensitive members. Particularly, nonmonocrystalline deposited films containing silicon atoms as the main component which are represented by amorphous silicon, for example, amorphous deposited films of amorphous silicon or the like compensated with hydrogen and/or halogen (for example, fluorine, chlorine or the like) have been proposed as pollution and contamination-free photosensitive members with high performance and durability. Some of them have been practically used. Japanese Patent Application Laid-open No. 54-86341 has disclosed a technique for electrophotographic photosensitive members the photoconductive layer of which is mainly formed with amorphous silicon.
A number of methods such as a sputtering method, a thermal starting gas decomposing method (thermal CVD method), an optical starting gas decomposing method (optical CVD method) and a plasma starting gas decomposing method (plasma CVD method) are known as methods for forming non-monocrystalline deposited films comprising silicon atoms as the main component.
The plasma CVD method, that is, a method for forming a thin deposited film on the substrate by decomposing the starting gas with a direct current, a high frequency or a microwave glow discharge, is best suited for formation of an amorphous silicon deposited film for electronic photography and practical application of this method has been substantially promoted. Particularly, lately, the plasma CVD method using decomposition by microwave glow discharging, that is, a microwave plasma CVD method has been industrially noted as the deposited film forming method.
The microwave plasma CVD method provides the advantages such as high deposition rate and high efficiency in use of the starting gas as compared with other methods. An example of microwave plasma CVD techniques which provide such advantages has been disclosed in U.S. Pat. No. 4,504,518. The technique disclosed in this patent is intended to obtain high quality deposited films at a high deposition rate at a low pressure of not higher than 0.1 Torr by the microwave plasma CVD method.
In addition, a technique for improving the efficiency of use of the starting gas by the microwave plasma CVD method has been disclosed in Japan Patent Application Laid-open No. 60-186849. The technique disclosed in this laid-open application is briefly intended to arrange a substrate so that it surrounds microwave energy introducing means and form an internal chamber (i.e. a discharging space), thereby substantially improving the efficiency of use of the starting gas.
Japanese Patent Application Laid-open No. 61-283116 has disclosed an improved microwave technique for making semiconductor members. In other words, this laid-open application has disclosed a technique which is intended to provide an electrode (bias electrode) for controlling a plasma potential in the discharging space, by applying a required voltage (bias voltage) and carrying out deposition of a film while controlling an ion impact to a deposited film, thus improving the characteristics of the deposited film.
When a cylinder made of an aluminum alloy is used as a substrate, the methods for making the electrophotographic photosensitive members according to the prior art are typically executed as described below.
A diamond cutting tool (trade name: MIRACLE BITE manufactured by Tokyo Diamond K.K.) is set on a lathe provided with an air damper for precision cutting (manufactured by PNEUMO PRECISION INC.) so as to obtain a relief angle of 5.degree. in reference to the central angle of the cylinder. Then the substrate is vacuum-chucked to the rotary flange of this lathe and mirror-finished at a peripheral speed of 1000 m/min. and a feed rate of 0.01 mm/R so as to obtain an outside diameter of 108 mm while spraying white kerosene from attached nozzles and removing used white kerosene which contains chip through attached vacuum nozzles.
Then each cut substrate is cleaned with trichloroethane to clear off cutting oil and chips remaining on its surface.
Each substrate is mirror-finished and cleaned, and a deposited film mainly comprising amorphous silicon is formed on the cleaned substrate by the deposited film forming apparatus for photoconductive members which uses a glow discharge decomposition method shown in FIG. 1.
In FIG. 1, a reactor 301 is formed by a base plate 302, a wall 303 and a top plate 304, wherein a cathode electrode 305 is provided and a substrate 306 on which an amorphous silicon deposited film is formed is arranged at the center of the cathode 305 to play a role of an anode.
For depositing the amorphous silicon film using this deposited film forming apparatus on the substrate 306, a starting gas inlet valve 307 and a leak valve 308 are closed, and exhaust valve 309 is opened to evacuate the reactor 301. The starting gas such as, for example, SiH.sub.4 gas, which has been adjusted to a predetermined mixing ratio in a mass flow controller 311, is introduced into the reactor 301 by opening the starting gas inlet valve 307 when a vacuum indicator 310 reads approximately 5.times.10.sup.-6 Torr. After it has been ascertained that a surface temperature of the substrate 306 is set at a predetermined temperature by a heater 312, a high frequency power supply 313 is set to a predetermined power level to cause glow discharging in the reactor 301.
While formation of a deposited film is being carried out, the substrate 306 is rotated by a motor 314 at a fixed speed in order to uniformly form the deposited film. Thus the amorphous silicon deposited film can be formed on the substrate 306.
However, in the conventional methods for making electrophotographic photosensitive members, there still remains a problem to be solved in that it is difficult to obtain, at a stable and high yield rate, deposited films capable of providing uniform qualities, satisfying optical and electrical characteristics and having high image qualities in formation of images by an electrophotographic process, particularly in an area where a depositing rate for forming the deposited film is high.
Specifically, a conventional electrophotographic photosensitive member includes a portion of abnormal deposition on which a surface charge of a micro area cannot be loaded. This phenomenon is especially observed on an electrophotographic photosensitive member prepared by the deposited film formed by the plasma CVD method such as amorphous silicon. However, such portion where a surface potential is unavailable can be minimized by optimizing the surface working conditions and the depositing conditions for the substrates. In the case of the prior art, such portions have been smaller than the resolution in development and therefore no problem has occurred in this point.
In recent years, however, the following situations have been noted.
1) High quality of images obtained by the electrophotographic apparatus has been demanded and accordingly the resolution of development has been improved.
2) Increasing of operating speeds of copiers has been promoted and charging conditions have been intensified to be more strict, and therefore those portions where the surface potential is unavailable have exhibited a substantial effect on the peripheral potential.
Under the situation as described above, these micro portions on which a charge cannot be loaded have been pointed out as a defect of the image though they have not been considered a problem.
In addition, since conventional copying applications have been mainly for the originals containing only characters (so-called line copies), these image defects have not actually been considered a serious problem. However, along with improvement of the qualities of copies made by the lately manufactured copiers, those scripts including half tone pictures such as photographs have increased to cause a problem. Particularly, these defects are visually clear in the color copiers which have widely been employed in recent years and are becoming a serious problem.
These changes are extremely small and cannot therefore be detected even though an electrode is provided at the upper part to measure the conductivity. However, when charging, exposure and development are carried out by the electrophotographic process for electrophotographic photosensitive members, particularly when a uniform image is formed in the half tone, even a slight difference of potential on the surface of the electrophotographic photosensitive members appears as visually remarkable defects. In particular, the above problem is more conspicuous in electrophotographic photosensitive members made by the microwave plasma CVD method.
On the other hand, such image defect will be particularly conspicuous on the electrophotographic photosensitive members made by the plasma CVD method as compared with the Se electrophotographic photosensitive members made by vacuum deposition and the OPC electrophotographic photosensitive members made by a blade application method or a dipping method.
In the case of the devices similarly made by the plasma CVD method, the difference of characteristics depending on the position on the substrate does not affect their performances as in solar cells, or the above described problem does not occur on the device which can be repaired by post treatment.